Evaluation of the Adsorption of Fluoride from Drinking Water by Modified Laterite for Northeast Ghana

Undergraduate #139
Discipline: Technology and Engineering
Subcategory: Water

Kimberly Cribbs - University of Arkansas – Fayetteville
Co-Author(s): Shola Falodun, Southern University and A&M College, LA

The World Health Organization’s recommended maximum value for the fluoride concentration in drinking water is 1.5 mg/L.1 Prolonged ingestion of water with a fluoride level >1.5mg/L can cause dental and skeletal fluorosis.1 Groundwater fluoride levels in northern Ghana range from 0.11 to 4.6 mg/L causing the closure of select boreholes.2 To address this issue, the Bongo District Assembly of northeast Ghana and local Community Water and Sanitation Agency approached Kwame Nkrumah University of Science and Technology (KNUST) in Kumasi, Ghana to develop a low-cost, sustainable fluoride absorbent. This preliminary study utilized 500-1000µm laterite, a locally available clay, as a base for fluoride adsorption. Alum and sodium hydroxide was used to precipitate Al(OH)3 on the laterite’s surface. The Al(OH)3 was converted to Al2O3 by firing the laterite at 400⁰C for 2 hours. Al2O3 reacts with fluoride to form AlF3. Unmodified laterite, the control, reduced the fluoride concentration in water from 5 mg/L to 3.44 mg/L after 35 minutes of contact. This study found that 10g of 500-1000µm laterite modified with 1g of alum saturated the surface of the laterite with Al2O3, reduced the fluoride concentration in water from 5 mg/L to 1.93 mg/L after 35 minutes of contact, and maintained an optimum pH within 5-7 for the adsorption of fluoride by Al2O3. Overall, this modification improved the laterite’s ability to adsorb fluoride ions from water. Future research involves studying the microstructural differences of the unmodified laterite and modified laterite pre and post fluoride adsorption using scanning electron microscopy with energy dispersive X-ray spectroscopy and altering the modification method to improve the laterite’s fluoride adsorption capacity.

References: [1] Lennon, M. A., H. Whelton, and et al. ‘Rolling Revision of the WHO Guidelines for Drinking-Water Quality Fluoride.’ World Health Organization, 1 Sept. 2004. Web. 14 July 2015. .
[2] Cumberbatch, Toby. “Design Considerations for an Indigenous Fluoride Filter for Use in Bongo, Ghana.” The Cooper Union for the Advancement of Science and Art (2005): 13-17. PDF. Lorem Ipsum

Funder Acknowledgement(s): National Science Foundation International Research Experiences for Students: U.S.-Ghana Collaboration Providing Opportunities for Global Research Activities on Sustainable Water Purification (GRA-SWP) Award Abstract #1358204, National Science Foundation Center for Research Excellence in Science and Technology.

Faculty Advisor: Patrick Mensah,